feat(data/fin): last

spl · Aug 23, 2018 · bd12c3f · bd12c3f
1 parent 58cfe9f
commit bd12c3f
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/data/fin.lean b/data/fin.lean
@@ -6,6 +6,12 @@ namespace fin
 
 variable {n : ℕ}
 
+/-- The greatest value of `fin (n+1)` -/
+def last (n : ℕ) : fin (n+1) := ⟨_, n.lt_succ_self⟩
+
+theorem le_last (i : fin (n+1)) : i ≤ last n :=
+le_of_lt_succ i.is_lt
+
 /-- Embedding of `fin n` in `fin (n+1)` -/
 def raise (k : fin n) : fin (n + 1) := ⟨val k, lt_succ_of_lt (is_lt k)⟩